This is the 2nd edition of "The Diamond Necklace" in Gregg Shorthand. It was published in 1923 and matches the 1916 Gregg Shorthand Manual. The Shorthand Plates were by Georgie Gregg Gingell. This version was serialized in the Gregg Writer Magazine June-Sept 1921.
There are 4 different Gregg Shorthand versions of "The Diamond Necklace":
--Pre-Anniversary 1902 - Serialized in Aug-Sept 1914 Gregg Writer - Never Published
--Pre-Anniversary 1916 - Serialized in June-Sept 1921 Gregg Writer - Published in 1923 - Plates by Georgie Gregg Gingell
--Anniversary 1929 - Minor modification - Slightly modified plates from 1923 Pre-Anniversary Edition. Book has same cover and line/page endings as 1923 version - Published March 1930
--Anniversary 1929 - Complete Revision - Completely revised plates by Winifred Kenna Richmond with standard green Anniversary cover - Published in 1933
This 1923 book entered the public domain as soon as it was first published. There is no copyright notice in the book. Any book first published in the US before January 1, 1978, without a proper copyright notice immediately went into the public domain at the time of publication. There are also no copyright notices in any of the other individual Gregg Shorthand novel versions of existing works, such as Alice in Wonderland, Rip Van Winkle, the Great Stone Face, etc. All copyrights belonged to the original material. Back then, the US Copyright Office did not allow Gregg to copyright shorthand novels based on existing literary works.